Thailand&rsquo;s wildlife community is abuzz after rangers at Kaeng Krachan National Park confirmed a rare sighting of the vividly purple &ldquo;Princess crab,&rdquo; locally known as the Chao Fa crab and identified by Thai outlets as Phricotelphusa sirindhorn. The park posted new images and updates in late July&ndash;August 2025, calling the encounter &ldquo;a precious gift from nature.&rdquo; The appearance at the end of the tourist season underscores how intact forest streams continue to shelter little-known invertebrates.<a href="https://thainews.prd.go.th/nbtworld/news/view/1249016/?bid=1&amp;utm_source=chatgpt.com">&nbsp;</a>
What exactly is the &ldquo;Princess crab&rdquo;?
Locally nicknamed for Princess Maha Chakri Sirindhorn, the crab&rsquo;s common name reflects the royal&rsquo;s long support for science and conservation in Thailand. Recent coverage from Thailand&rsquo;s public broadcaster and international outlets ties the sighting to Kaeng Krachan, a UNESCO-listed forest complex famed for its high biodiversity.<a href="https://thainews.prd.go.th/nbtworld/news/view/1249016/?bid=1&amp;utm_source=chatgpt.com">&nbsp;</a>
<h2 dir="ltr">Habitat and behaviour</h2>
Field notes indicate the Princess crab favours cool, shaded, rocky creeks and splash zones around waterfalls, often hiding beneath stones. Observations place it at roughly ~100 m elevation in clean, oxygen-rich flows. Because it occupies narrow ribbons of habitat, the species is sensitive to pollution, water abstraction, trampling at stream crossings, and sediment runoff. It has been listed for protection under Thailand&rsquo;s Wildlife Preservation and Protection Act since 2019.<a href="https://www.bangkokpost.com/thailand/general/3064006/rare-panda-crab-spotted-in-western-thai-forest?utm_source=chatgpt.com">&nbsp;</a>
Why is it purple?
Crab shell colours are largely driven by carotenoid pigments, especially astaxanthin, bonded to proteins called crustacyanins. When astaxanthin binds within these carotenoprotein complexes, its light-absorption spectrum shifts, producing blues, purples, and other hues in live crustaceans (heat cooking later releases the red pigment). Studies in lobsters and other crabs show that differences in carotenoid content, binding strength, and protein structure can generate striking purple morphs. Additional accessory pigments (e.g., ommochromes) and microstructure can further modulate the final colour. In short: genetics + diet-derived carotenoids + shell proteins = royal purple.<a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC8143343/?utm_source=chatgpt.com">&nbsp;</a>
Biologists regard the Princess crab as an &ldquo;indicator&rdquo; of pristine headwater health: if the tiny, secretive stream dweller is present, the microhabitat is likely cool, clean, and undisturbed. Thailand&rsquo;s Department of National Parks celebrated the 2025 photographs as evidence that conservation work inside Kaeng Krachan is sustaining such micro-refugia. For visitors, the message is simple: admire, don&rsquo;t disturb, stick to trails, avoid rock-turning, and never collect wildlife.<a href="https://www.popsci.com/environment/purple-crabs-thailand/?utm_source=chatgpt.com">&nbsp;</a>
The Princess crab is small, semi-terrestrial, and associated with splash zones; it is not the same as the pet-trade &ldquo;panda crabs&rdquo; from Borneo that share a black-and-white pattern. Thai reports for this sighting point specifically to Phricotelphusa sirindhorn in western Thailand&rsquo;s Kaeng Krachan. That distinction helps prevent mislabeling and illegal collection.
Protecting narrow riparian corridors is crucial: simple measures buffering streams from road dust and runoff, regulating visitor access around waterfalls, and keeping tourism infrastructure set back from creek lines, can safeguard the Princess crab&rsquo;s niche. Continued monitoring by park staff and citizen scientists (photos, geotags withheld from public posts) can build a baseline for future management.

Rangers spot rare “Princess crab” in Thai park

Rare Purple Princess Crab Found in Thailand, 2025!

Rangers spot rare “Princess crab” in Thai park

August 14, 2025 | 22:00 IST